The present invention generally relates to a hydrostatic radial piston pump.
Hydrostatic radial piston pumps are known in the art. One of such piston pumps is disclosed, for example, in the German Auslegeschrift 2,716,888. It has an eccentric, a pressure valve member with a convex support, and a movable structural unit arranged between the eccentric and the pressure valve member and having a cylinder with supporting face and a sealing edge spring-biased against the support of the pressure valve member, and a piston with a piston shoe spring-biased against the eccentric. In the above described radial piston pump, the supporting face with the sealing edge of the cylinder abutting against the support of the pressure valve member is so dimensioned that the pressure force of a pressure spring providing the above mentioned spring-biasing action is transmitted from the supporting face to the support in a wear-free manner. It is necessary to take into consideration that the lifting force which takes place during the pressure stroke resulting from the hydrostatic pressure acting between the support and the supporting face is smaller than the pressure force acting outwardly for a reliable sealing of this cylinder space. In addition to the spring force, a hydrostatic force acts also as a pressing force in direction from the support of the pressure valve member to the cylinder. The hydrostatic pressing force results from the respective dimensioning of the inner diameter of the sealing edge of the cylinder. The smaller this diameter is selected relative to the piston diameter, the greater is the hydrostatic pressing force acting in direction of the support. The greater, however, is the weight of the supporting face of the cylinder on the support of the pressure valve member, the greater is the danger of a dry friction during the suction stroke of the pump, particularly when low viscosity fluids are utilized for the pump.